1. Field of the Invention
This invention directs itself to a flue gas conditioning system for adding sulfur trioxide to a flue gas stream in order to substantially optimize the particulate removal efficiency of an electrostatic precipitator coupled to the flue. In particular, this invention directs itself to a system for adding sulfur trioxide to a flue gas responsive to a control signal proportional to measured characteristics of the flue gas. Still further, this invention directs itself to a system which accurately determines a deficiency in sulfur oxide content of a flue gas by measuring the sulfur dioxide/content of the flue gas and the flow rate of the particulates carried thereby. Further, this invention directs itself to a control system which generates a control signal proportional to the ratio between the two measured flue gas characteristics and utilizes that control signal for controlling the feed rate of sulfur to a reaction chamber wherein sulfur dioxide is formed and subsequently converted to sulfur trioxide for injection into the flue gas.
2. Prior Art
Systems for conditioning flue gas with sulfur trioxide to aid in particulate removal in electrostatic precipitators are known in the art. The best prior art known to the Applicant include U.S. Pat. No. 3,993,429. In such prior art systems sulfur trioxide is added to the flue gas for conditioning thereof responsive to a control signal representing the operating parameters of the boiler generating the flue gas. In such systems the injection of sulfur trioxide into the flue gas is controlled by measuring boiler load signal, representing boiler operating conditions in combination with assumption made about the ash and sulfur content of the coal being burned. This control signal is utilized to control the rate at which sulfur is supplied to the reaction chamber. Such systems fail to accurately supply sulfur trioxide to the flue gas, since they fail to utilize a measurement of the sulfur dioxide content of the flue gas. Further, such prior art systems do not provide any means for measuring the particulate content of the flue gas whereby the ratio of the particulates to sulfur oxide content can be computed for defining a sulfur feed rate to the reaction chamber which accurately results in sufficient sulfur trioxide being added to the flue gas to optimize the electrostatic precipitator performance without releasing sulfur oxides to the atmosphere.